As a nurse I can tell you that is a very dangerous thing to do, and one little mistake can kill you. I also agree with the above post, you are on the wrong web site to ask a question like that. I hope that you will realize that you are on a road of destruction but there are alot of people on here that will help you to get clean.
Listen, everyone here r either working to get in recovery or in recovery, u posting this can trigger sume1 to have a relapse. I was addicted to pain pills ( never injected only snorted pills) and seeing ur post triggered those old feelings. I can't imagine what ur post makes a recovering heroin addict feel like. I hope u don't get upset about my postting this. I just needed to let u know.